Second receptors which the pathogenic virus causative of AIDS (HIV-1 virus) utilized in infecting human were identified in 1996 (Yu Feng et al., Science, 272, 872-877, 1996). These receptors are two receptors called CXCR4 and CCR5 among the chemokine receptors already reported. It has been revealed that the HIV-1 virus utilizes one of the receptors for adsorption onto and entry into human lymphocytes, macrophages and dendritic cells to achieve infection.
On the other hand, about 1 to 2% of Caucasians reportedly have resistance to HIV-1 virus infection and it has been revealed that this is due to a genetic defect or genetic incompleteness of the second receptors (CXCR4 and CCR5), which are chemokine receptors (Hong Liu, et al., 86, 367-377, 1996).
These findings have called researchers' attention to the importance of neutralization of the second receptors in the prevention of HIV-1 virus infection and, in recent years, attempts have been made to produce a neutralizing antibody capable of neutralizing the second receptors. There is no report, however, about the successful creation of such a neutralizing antibody.
Accordingly, it is an object of the present invention to provide three-dimensional antigens capable of producing, in vivo, a neutralizing antibody capable of neutralizing the second receptors from the three-dimensional viewpoint by paying attention to the loop structures of the second receptor proteins without employing the conventional techniques of interpreting the peptides constituting the second receptors two-dimensionally. Another object is to provide AIDS vaccines which comprise such antigens as active ingredients.